Adaptive Coding and Modulation (ACM) is a technology of adaptively changing a modulation scheme and an Forward Error Correction (FEC) coding scheme according to a channel status.
A core idea of the ACM is to obtain a relatively large throughput under the premise of not increasing a bit error rate, according to different requirement scenarios, by dynamically changing transmit power, a baud rate, a size of a constellation diagram, a coding scheme, a bit rate, and the like of a transmit end, in a relatively good channel condition, and by using higher order modulation and high bit rate FEC coding. When channel quality deteriorates, a system lowers a modulation order and uses low bit rate FEC coding, so as to lower a transmission rate to ensure transmission quality. In the prior art, the ACM is mainly implemented by using FEC codes of different lengths as the modulation order changes.
In the foregoing process in which the ACM is implemented, the inventor finds that the prior art has the following problems: To ensure smooth switching between different modulation and coding modes, an adaptive modulation and coding system needs to compatibly implement coding and decoding for different FEC code lengths and FEC bit rates, which consumes resources. In addition, when the adaptive modulation and coding system is upgraded, a higher-performance FEC code needs to be used or a modulation mode needs to be added, and all FEC codes of different lengths need to be re-designed in the prior art, which reduces system upgrade flexibility.